Add mir opt tests to be sure we generate copy, clones and moves when corresponds

tests/mir-opt/ergonomic-clones/closure.rs

@@ -0,0 +1,55 @@
+#![crate_type = "lib"]
+#![feature(ergonomic_clones)]
+#![allow(incomplete_features)]
+
+use std::clone::UseCloned;
+
+pub fn ergonomic_clone_closure_move() -> String {
+    // CHECK-LABEL: fn ergonomic_clone_closure_move(
+    // CHECK: _0 = move (_1.0: std::string::String);
+    // CHECK-NOT: <String as Clone>::clone
+    let s = String::from("hi");
+
+    let cl = use || s;
+    cl()
+}
+
+#[derive(Clone)]
+struct Foo;
+
+impl UseCloned for Foo {}
+
+pub fn ergonomic_clone_closure_use_cloned() -> Foo {
+    // CHECK-LABEL: fn ergonomic_clone_closure_use_cloned(
+    // CHECK: <Foo as Clone>::clone
+    let f = Foo;
+
+    let f1 = use || f;
+
+    let f2 = use || f;
+
+    f
+}
+
+pub fn ergonomic_clone_closure_copy() -> i32 {
+    // CHECK-LABEL: fn ergonomic_clone_closure_copy(
+    // CHECK: _0 = copy ((*_1).0: i32);
+    // CHECK-NOT: <i32 as Clone>::clone
+    let i = 1;
+
+    let i1 = use || i;
+
+    let i2 = use || i;
+
+    i
+}
+
+pub fn ergonomic_clone_closure_use_cloned_generics<T: UseCloned>(f: T) -> T {
+    // CHECK-LABEL: fn ergonomic_clone_closure_use_cloned_generics(
+    // CHECK: <T as Clone>::clone
+    let f1 = use || f;
+
+    let f2 = use || f;
+
+    f
+}